The current grant proposal addresses NIA PAR-03-056 research topic area to "Improve Health and Quality of Life of Older People", number 12, "Factors Moderating Rate of Age-related Changes and Risk for Adverse Events with Increasing Age". By the year 2030 the population of Americans aged 65 years or older is projected to reach 70.3 million, then representing approximately 20% of the population. As life expectancy continues to increase, it is necessary to better understand factors underlying age-related changes in physiology and behavior and to identify risk factors for adverse events that increase with age. Falls are a serious health concern among older adults, as falls are the leading cause of injuries in people over 65 years of age. Over 1/3 of older adults fall each year and over 50% of these adults have recurrent falls. We propose to examine the influence of age, awakening from sleep (sleep inertia) and of hypnotics on gait stability during walking to improve our understanding of these factors in the risk of falls in older adults. The purpose of the proposed study is to test 2 specific hypotheses aimed at evaluating the effects of sleep inertia, hypnotics, and age on gait stability while walking and on cognitive performance. These 2 hypotheses are as follows: Test the hypothesis that i) sleep inertia will impair gait stability and cognitive performance upon awakening from sleep more in older adults than in younger adults; ii) hypnotics use will impair gait stability and cognitive performance upon awakening from sleep more in older adults than in younger adults. The results of the proposed research could have a significant impact on the health, safety and quality of life of older adults.